The punch of German Utility Model DE-GM 7228225 has a control mechanism for the displacement of a punch tool carriage.
The punch comprises a machine frame, a punch tool carriage which is movable up and down in the machine frame, a die-bearing or anvil member having a workpiece receiving portion fixed in position relative to the machine frame positioned opposite the punch tool carriage and a stripper mounted on the machine frame and adjustable in height for different workpiece thicknesses.
The control mechanism has a plurality of controlling element pairs including a plurality of control cams and associated control switches. One controlling element of the controlling element pairs is mounted on the punch tool carriage while the associated controlling element is mounted on a portion of the machine frame.
The height adjustability of the stripper can be provided in different ways (see, for example, German Utility Models, 72 28 225, 74 25 321).
In the known punch machine described above on which the invention is based, i.e. on German Utility Patent 72 28 225, the controlling mechanism acts so that the downward directed working stroke of the punch carriage is limited and the motion of the punch tool carriage reverses at a lower dead point for the return stroke.
A control cam is mounted on the punch tool carriage and a control switch is mounted on a holder which is attached to the machine frame. Generally a suitable design limits the uppermost position for the punch tool carriage.
The described arrangement for the control of the lower turning point of the working displacement is such that the stripper is adjustable independently of it, so that its height adjustment has no influence on control of the punch tool carriage stroke.
Punch machines of the above-described structure are designed to receive punch tools with different lengths in the punch direction. The uppermost position for the carriage is suitably adjusted and this adjustment does not take into consideration the height of the stripper which is different according to different workpiece thicknesses. As a result the displacement, i.e. the distance between the lower turning point and the upper turning point, is not optimized and not easily adjustable to the described different working parameters, namely the workpiece thickness and the displacement of the punch tool.
By "displacement" or "stroke" of the punch tool or its carriage I mean the distance traveled in one direction by the punch tool or its carriage during a single punch stroke.